Thanks for the explanation of the prop and drive ratio. That clears
up a bunch. How does Tracy get past the brick wall thing with his
drive ratio? Can he maintain 200mph? Can't imagine a rotary going
that fast! I like that! Skip

He may have a bit more power than most. He runs 6300 RPM max
as I recall. Perhaps his prop is a bit less pitch or diameter.
I also think he would agree his prop pitch is less than optimum.
His engine has the 1993 turbo big port end and center housings with
the earlier high compression rotors as I recall. Bruce Turrentine
built it. Perhaps it has a mild street port. Tracy is also using a
tuned intake manifold on the dynamic chamber principle.

If Tracy changed to a 2.85 to one PSRU ratio IMHO he probably would be
seeing around 210 MPH and 8,000 RPM.

Paul Lamar

I seem to remember that Tracy is turning up to 6500 engine RPM which is 2995
prop RPM.  If he is running a 68" dia prop (normal for a RV-4), he is probably hitting
the upper tip speed limits for a clark-y airfoil.  This problem is worse at altitude since
the speed of sound decreases with altitude.  This is verified by both the John Ronc
and Joe Dubner prop sim programs.  I'm waiting on Tracy's 2.85 redrive just for this
reason;  2596 prop rpm equals 7400 engine rpm - gotta have the HP like a true
gearhead!  In a previous conversation with Tracy, he favors the 2.17 redrive and the
high prop rpm that goes with it.

Ken Powell

 
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